Cellular radiotelephone systems are commonly employed to provide voice and data communications to a plurality of subscribers. For example, analog cellular radiotelephone systems, such as designated AMPS, ETACS, NMT-450, and NMT-900, have been deployed successfully throughout the world. More recently, digital cellular radiotelephone systems such as designated IS-54B in North America and the pan-European GSM system have been introduced. These systems, and others, are described, for example, in the book titled Cellular Radio Systems by Balston, et al., published by Artech House, Norwood, Mass., 1993.
Multiple cellular radiotelephone systems may be controlled by a common cellular operator. For example, in a large geographic area, multiple cellular radiotelephone systems may be under control of a single cellular operator. Moreover, with the advent of microcell technology, a microcellular radiotelephone system may be included within the geographic coverage of a macrocellular radiotelephone system and controlled by a common cellular operator. Finally, a Wireless Office System (WOS) may be located in a building to provide cellular radiotelephone communication among cellular radiotelephones that are located in the building. The Wireless Office System may be operated by the common cellular operator for the geographic area in which the Wireless Office System is located.
When a common cellular operator controls multiple cellular radiotelephone systems, communications generally take place between the common cellular operator's cellular operator system and the multiple cellular radiotelephone systems. More specifically, communications may take place between the central service node of a cellular operator system and the Cellular Radio Exchange (CRE) of each of the cellular radiotelephone systems.
These communications may allow the cellular operator to control the frequency allocation among the cellular radiotelephone systems, so as to reduce interference. These communications may also allow the cellular operator to deactivate a selected one of the cellular radiotelephone systems, for example due to nonpayment of bills by the owner of the selected cellular radiotelephone system. For example, when a cellular operator controls many Wireless Office Systems, it may be desirable to allow the cellular operator to deactivate one or more of the Wireless Office Systems upon nonpayment of bills.
Conventionally, deactivation of a cellular radiotelephone system by a cellular operator system is accomplished by sending a deactivation message from the cellular operator system to the selected cellular radio exchange. The deactivation message may be sent by electronic mail (email) using Transmission Control Protocol/Internet Protocol (TCP/IP). As is well known to those having skill in the art, the TCP/IP communications protocol utilizes an IP address to route messages between networked computers and networks of networked computers. The TCP/IP communications protocol is well known to those having skill in the art, and need not be described further herein.
Generally, a cellular radiotelephone system may be deactivated by the cellular operator by sending a "shut down" message in an email via TCP/IP communications protocol or by failing to send a "keep alive" message in an email via the TCP/IP communications protocol. Each of these deactivation techniques will now be described.
Referring now to FIG. 1, the sending of a "keep alive" message via a TCP/IP communications protocol email will now be described. As shown in FIG. 1, a cellular operator system 100 controls a plurality of cellular radiotelephone systems 120a-120n. The cellular operator system includes a central service node 102. Each cellular radiotelephone system 120a-120n includes a cellular radio exchange 122 that communicates with a plurality of base stations, also referred to as radio heads (RH) 124 in a plurality of cells 126. A plurality of cellular radiotelephones, not shown in FIG. 1, communicate with the radio heads 124 in the cells 126. In FIG. 1, the cellular radiotelephone systems are Wireless Office Systems that are located on a floor 130 of an office building. However, the cellular radiotelephone systems 120a-120n may be other conventional cellular radiotelephone systems.
Still referring to FIG. 1, in order to deactivate a selected cellular radiotelephone system 120a-120n, the central service node of the cellular operator system 100 sends a "keep alive" email message to the cellular radiotelephone systems 120a-120n except for the selected cellular radiotelephone system, using a TCP/IP line 150a-150n, and withholds the "keep alive" message from the cellular radio exchange 122 of the selected radiotelephone system. The TCP/IP email links 150a-150n may be the internet, an intranet, a dial-up modem or any other TCP/IP-based link.
Stated differently, the cellular operator system 100 identifies cellular radiotelephone systems that have and have not paid their bills. The central service node 102 sends a "keep alive" message as an encrypted TCP/IP email via TCP/IP communication links 150a-150n, to those cellular radiotelephone systems that have paid their bills.
FIG. 2 is a flowchart illustrating a "keep alive" function at the cellular radio exchange 122. As described in FIG. 2, the cellular radio exchange waits for a predetermined time, for example 12 hours, at Block 202. A determination is then made at Block 204 as to whether the "keep alive" message was received. If yes, then the grace period is set, for example to 48 hours, at Block 206. If the "keep alive" message was not received, then 12 hours is deducted from the grace period at Block 208. If the grace period becomes zero at Block 210, then the cellular radiotelephone system shuts itself down at Block 212. If the grace period is not zero, then the "keep alive" function returns to Block 202 to wait another 12 hours. Accordingly, if a cellular radiotelephone system 120a-120n receives the "keep alive" message, it is allowed to stay in operation. If not, the cellular radiotelephone system shuts itself down after a fairly long grace period.
Unfortunately, the use of a "keep alive" message may cause cellular radiotelephone systems that have paid their bills to inadvertently deactivate if one or more "keep alive" email messages are not properly received by the cellular radio exchange 122. For example, the internet or other TCP/IP link may be down, or the cellular radio exchange may not receive TCP/IP email for a long period of time.
FIG. 3 illustrates a second conventional technique for deactivating a cellular radiotelephone system that has not paid its bills, by sending a "shut down" email message via a TCP/IP links 150a-150n. As shown in FIG. 4, when a "shut down" message is received at Block 402, the cellular system deactivates itself at Block 404. Accordingly, inadvertent shutdown of a cellular radiotelephone system that has paid its bills may be prevented.
Notwithstanding the above discussion, there continues to be a need for improved systems and methods for deactivating a cellular radiotelephone system by a cellular operator system, for example for nonpayment of bills.